With such a wide development of fortifications by means of flanking towers, extending from the cultural spheres of the Babylonians and the Hittites over all the western parts of Asia, and carried by the Phoenicians into the furthest limits of the Mediterranean, it is not surprising that the fortifications of Greek towns in the fifth century should exhibit the same features. Assos, the finest example of this period, carries on the tradition in the crémaillères and rectangular towers of its walls;[232] and Messene, with its rounded and rectangular towers, shows in the succeeding century a yet more complete understanding of military architecture.[233] The acropolis of Selinus, with semicircular towers, bears witness at a like age to the carrying over of the Greek system of defences into Sicily.[234] The walls of Ephesus, built by Lysimachus towards the close of the third century, ‘one of the greatest monuments of fortification which have been left to us by antiquity,’[235] show the towered wall of the Hellenistic age, while Mantineia, with its circular outer wall, is like an isolated reversion to the round cities of Hittite lands.[236] Philon of Byzantium formulated the laws which governed Greek fortification in the Alexandrian age. Towers, crémaillères, and casemated walls combined to make a system of defence all the elements of which had been familiar to the Hittites and to the Assyrians, and the methods of attack which he sought to counter were the same as those which can be seen on the Assyrian reliefs.[237] Vitruvius advocates the flanking of walls by round or polygonal rather than by rectangular towers, but his words should be taken as a counsel of perfection, not as representing the practice of his day, for the systematic use of rounded towers by Roman engineers is later than Augustan times and polygonal towers are unusual before the age of Diocletian. At Aosta, which was fortified soon after 25 B.C., the towers are rectangular,[238] but at Fréjus and at Autun, both of which were fortified in the Augustan age, we have two of the rare instances of circular or semicircular towers.[239] As Schultze has pointed out, the planning of towers varies with time and place, but not infrequently rounded and rectangular towers can be seen on buildings of the same date.[240] As at Zindjirli the rounded tower denotes a technical advance, though the rectangular tower is not necessarily displaced by it. The typically Roman conception of frontier defences, the fortified limes, was definitely abandoned in Europe about the year A.D. 360, but a century earlier the invasion of Gaul and Spain by the Franks had proved that the long line of strongholds was powerless to check the inrush of barbarian hordes, and in the last half of the third century the fortified town was virtually substituted for the fortified frontier. Towered walls sprang up about the cities of Roman Gaul, and the work of fortification begun by Probus was carried on by Diocletian.[241] The same process can be observed throughout the empire during the course of the third century, and almost without exception these later fortifications were strengthened by circular or semicircular towers.
But if the walls of Roman cities can claim to have inherited, through Greece and the civilizations of the Aegean, the formulae of the ancient East, the fortified camp was essentially the creation of Rome herself. The stockaded earthwork, with rounded corners and lines devoid of flanking defences, determined the plan of the stone wall which replaced it in Europe and in Africa,[242] and it was not until the Romans applied their system to lands which had seen the birth and development of a science of warfare different from their own that they modified their design. The difference was fundamental. The Roman camp was intended primarily for purposes of attack. It was the camp of an army on the march, indispensable, in the eyes of commanders as wary as they were daring, to a halt that lasted no longer than a single night, but in its essence impermanent. The oriental fortress displays a contrary intention. It was defensive and abiding, a stronghold provided with few exits (since the gateway is the weakest point of a fortified position), but with high walls, heavily flanked by towers which would give the garrison every advantage against the besiegers.
By the time of Diocletian the transition upon the Arabian limes from camp to fortress had been completed. The Umayyad khalifs, when they in turn strewed the fringes of the Syrian desert with the creations of their architects, copied, not the Roman plan which had been imported under Trajan and had survived, in broad outline at any rate, at least, as late as the year A.D. 162 (the date of Ḍumair), they copied its oriental counterpart, adapting it to the use of princes by methods borrowed from Byzantium and from Persia. We know that the Umayyads, like the Ghassânids before them, repaired and re-occupied the Roman fortresses. Hamza al-Iṣfahâni believed that Qasṭal and Odhruh had been built by Djabala ibn al-Ḥârith;[243] Yâqût mentions that Yazîd ibn ‘Abd al-malik (Yazîd II) lived at Muwaqqar, and judging from the existing remains it is probable that he either built or rebuilt it.[244] His son Walîd occupied Qastṭal and Azraq.[245] But princes whose passion for magnificent construction was so great that the subjects of Yazîd III could see cause for exacting from him, when he came to the throne, a promise that he would not lay stone to stone or brick to brick,[246] were not likely to content themselves with the forts of the Roman limes. The poets, who were welcome guests at their palaces in the wilderness, have left descriptions of the luxury of their surroundings,[247] and the picture has been completed by the discovery of some of the buildings themselves. None of the ruins which have been examined are mentioned by contemporary writers under the name by which they are known to the Beduin, but a palace or palaces are recorded in the Wâdi Ghadaf, and it is in that district that Ṭûbah, Kharâneh, and Qṣair ‘Amrah stand.[248] Mshattâ, which was the first to be visited by archaeologists, bears a name which is probably modern.
Qṣair ‘Amrah lies somewhat outside the architectural type to which the other three buildings belong. It is a small unfortified pleasure-palace with a reception hall and throne-room on a basilical plan, and a bath. Very closely related to it is the early Mohammadan ruin of Ḥammâm al-Ṣarakh, discovered by the Princeton Expedition.[249] The bath at Djebel Sais is not dissimilar, but in the light of our present knowledge it requires re-examination.[250] Both at Qṣair ‘Amrah and at Ḥammâm al-Ṣarakh there is a small dome over a square chamber. At Ḥammâm al-Ṣarakh this chamber is 2·15 metres square; the dome is set on pendentives and lighted by windows. It is laid up in gores with projecting ribs constructed of long, thin, wedge-shaped bits of shale, entirely undressed and completely covered by plaster. When intact it must have presented an appearance not unlike that of the ribbed dome at Ukhaiḍir, except that the ribs were set wider apart and the pendentive substituted for the primitive bracket. Concerning the structural features of the dome at Qṣair ‘Amrah, the publication of the Viennese Academy, which leaves much to be desired, is not explicit. Dr. Musil, who is always the best guide in matters architectural and archaeological, describes it as being set on pendentives and lighted by windows in the dome.[251] Here and at Ḥammâm al-Ṣarakh two semi-domed niches are placed opposite to one another, one at either end of the domed chamber, and a room (3·30 metres square at Ḥammâm al-Ṣarakh) next to the domed chamber is roofed with a groined vault. We have a similar use of the groined vault in the east annex at Ukhaiḍir. At Ḥammâm al-Ṣarakh some of the doors are covered by straight lintels, others (together with all the windows) by semicircular arches. Some of the wider arches are slightly pointed, but the vaults and transverse arches in the reception-room are semicircular. At Qṣair ‘Amrah straight lintels are the rule for doors and windows, but over the architrave of the wide door leading into the audience chamber there is a shallow relieving arch. The three parallel barrel vaults of the audience chamber are visible upon the exterior, and the absence of the flat roof obviates the need of tubes between the vaults. In both of these bâdiyahs the walls were decorated with frescoes. Qṣair ‘Amrah was built between the years 711 and 750, when the house of Umayyah came to an end, the earlier date being determined by the presence among the frescoes of a representation of Roderick, the last king of the West Goths, who came first into contact with the Arabs at the battle of Xeres in 711.[252]
To the same group belong a small ruined bath at ‘Abdeh[253] and the bath at Rḥaibeh,[254] the first being possibly Byzantine. At ‘Abdeh the dome placed between two semi-domed niches is set on horizontal brackets. In the palace of Qaṣr ibn Wardân the dome between two semi-domed niches is the basis of the plan, but it is further elaborated by the placing of a semi-domed chamber on the alternate sides. These two chambers are not, however, an integral part of the domed chamber, for they are separated from it by solid walls broken only by doorways. Fortunately we are not reduced here to conjecture concerning the date. On the lintel of the south gate an inscription gives the year A.D. 564.[255] It is clear, therefore, that the dome between semi-domed niches is an architectural scheme which was taken over by the builders of the Mohammadan age from their Byzantine predecessors, and all the evidence points to the conclusion that in both periods the artificers were Syrians.
Al-Ṭûbah is the southernmost of the Wâdi Ghadaf palaces[256] ([Fig. 28]). Its plan is that of Qasṭal repeated three times, with the addition of projecting rectangular chambers on either side of the gates. When the three main courts adjoin one another the side chambers against the dividing walls are omitted. The individual baits are very similar to those of Qasṭal, but only one row of chambers is interposed between each of the small courts. Thus at first sight it looks as if the Ṭûbah bait consisted of a court with rooms on one side only, except in the north-east and north-west angles, where the courts have chambers on both sides, that the corner spaces may be filled in. Actually, however, the
Fig. 28. Ṭûbah. (From Qṣeir ‘Amra, by kind permission of the Akad. der Wiss. in Vienna.)
bait centres round each alternate court, which communicates with the two chambers on either side, and the intermediate court is merely a yard common to two baits. The bait of Ṭûbah is therefore the same as the typical bait of Qasṭal. The enclosing walls and the foundation of all other walls are of stone, the rest of the building is constructed of brick tiles. The western end of the palace, and most of the northern side were completed; the eastern and south-eastern parts were never carried above the foundations. The doorways are covered by brick and stone arches, but a stone or wood lintel was placed under the arch. Where the lintel is of stone its outer side is adorned with an interesting early Mohammadan pattern, which has affinities with the carving on the eastern end of the façade at Mshattâ. The stone lintels are not carried through to the inner side of the arch. The arches, which are round, are built of stone, as is the wall below them. The wooden lintels have rotted away or have been removed by the Arabs. They were laid in brick walls and covered by brick relieving arches composed of two rings of brick tiles. In the inner ring the bricks are set vertically, parallel to the main axis of the arch, with the broad side outwards; in the outer ring they are laid horizontally, at right angles to the main axis, with the narrow end outwards. It is the principle on which many of the smaller arches at Ukhaiḍir are constructed. The brick arches at Ṭûbah are a stilted, slightly pointed oval; that is to say that the transition from the ovoid to the pointed arch is illustrated here in much the same manner as at Ukhaiḍir.